Piers Morgan: "The Queen's a year older than The Pope. Can't see her ever resigning because she's tired. #indefatigability"

Kirstie Alley: "hope the Pope isn't sick. I'm not Catholic but it still feels sad..is there a successor like a VP in USA or Prince in UK?"

Ricky Gervais: "Being 'The Pope' means you are married to God. So, is this like a divorce?" And: "Pope resigns and moves into Broadhill Nursing Home. 'They have discos & everything' he said." And: "Haha. I'm flattered, but I seriously doubt this will trend...#RickyGervaisForPope."

Joyce Carol Oates: "To some, the Pope is godly authority. To others, the Pope is somewhat comical. And to others, a terrifying figure of misinformation & harm."

Kevin Smith: "From now on, when someone snarks you with 'Is the Pope Catholic?' you can say 'He's not even the Pope anymore...'"

Jim Gaffigan: "Wow the Pope is not taking my Grammy loss very well."

Simon Pegg: "I bet he gets one really dangerous assignment, just before he retires, like a civil war or an exorcism. #pope"

Mia Farrow: "The last time a pope willingly resigned was in 1294 Hoping for a more progressive successor - imagine a pope more like Arch Desmond Tutu"

Star Jones: "PROOF twitter can tire anyone out. Even the #VicarOfChrist.> '#PopeBenedict was the first #Pope to be on Twitter."